It is frequently desirable to deposit a metal on the surface of a metallic article. This depositing or plating may be needed to restore the original dimensions of the article if the surface has been eroded or improve the wearing or corrosion protection properties of the surface. Typically the plating is accomplished using an electroplating process.
There are many different ways in which the electroplating process may be carried out. If the entire article is to be plated, tank electroplating may be used. In tank electroplating, the article to be plated is electrically connected to act as a cathode and placed in a tank filled with an electroplating solution.
A potential difference is then applied between the cathodic workpiece and an anode, and metal ions from the solution are plated on the article. Concurrently, metal atoms from the anode are converted to metal ions, which dissolve in the electrolytic solution, thereby replenishing the metal content of the solution.
Tank electroplating is not efficient when only a portion of the workpiece is to be plated. To accomplish partial electroplating the other areas of the workpiece must be masked. However, this increases the labor requirements.
To perform electroplating of limited surface areas, a procedure known as brush electroplating was developed. The brush plating apparatus typically employs an anode which is wrapped in an absorbent tool cover material or felt to form a brush. The brush is rubbed over the surface to be plated and an electrolytic solution is injected into the absorbent tool cover material. The electrolytic solution includes metal ions, of the metal to be deposited on the workpiece,, in the form of soluble compounds.
In brush electroplating, soluble anodes, which are composed of the metal to be plated, are not used because the absorbent cover material interferes with efficient agitation of the solution at the anode surface. The interference causes metallic ions to collect at the surface of the anode which polarizes the anode. A polarized anode generally cannot adequately perform the process of electroplating.
Therefore, in brush electroplating insoluble anodes are used. The anodes are typically constructed of graphite, platinum plated or clad titanium or niobium. However, the insoluble anode cannot contribute metal ions for the plating process. Thus the metal ions must be supplied solely from the electrolytic solution. As the metal ions in the electrolytic solution are used, the electrolytic solution becomes depleted and must be replaced. The depleted electrolytic solution must then be disposed of. This depleted electrolytic fluid is typically classified as a hazardous substance; and therefore, disposal of the fluid poses a drawback to using brush electroplating techniques.
It is therefore an object of the present invention to provide an improved method and apparatus for electroplating metallic surfaces and more particularly to providing a method and apparatus for electroplating using brush-type anodes.
It is a further object of the present invention to provide an improved method and apparatus for brush electroplating which reduces the amount of electrolytic fluid depleted during the electroplating process.
It is a still further object of the present invention to provide an improved brush electroplating device which employs soluble anodes.